In typical cellular wireless communication systems, wireless communication devices (e.g., cell phones, personal digital assistants, laptops, netbooks, tablets, and/or other wirelessly equipped devices, any of which may be referred to as a user equipment (UE) for brevity) subscribe to service from a given cellular wireless service provider. In practice, a service provider will operate one or more networks (sometimes referred to as radio access networks (RANs)) including base stations that radiate to define wireless coverage areas where the subscriber UEs can operate.
Through each base station (and corresponding RAN), a UE can obtain connectivity to other networks such as the public switched telephone network (PTSN) and the Internet. Further, each RAN may include one or more radio network controllers (RNCs), mobility management entities (MMEs), or the like, which may be integrated with or otherwise in communication with the base stations, and which may include or be in communication with a switch or gateway that provides connectivity with one or more transport networks. Conveniently with this arrangement, a UE that is positioned within coverage of the RAN may communicate with a base station and in turn, via the base station, with other served devices or with other entities on the transport network.
Generally, wireless communications between a given UE and a serving base station in a RAN are carried out in accordance with one or more air interface protocols that define a mechanism for wireless exchange of information between the UE and the base station. Typically, an air interface protocol will define a “forward link” encompassing communications from the base station to the UE and a “reverse link” encompassing communications from the UE to the base station. Further, each of these links may be structured to define particular channels on which certain types of data may be transmitted. These channels may be defined through the use of various mechanisms, including for example, time division multiplexing, code division multiplexing (e.g., spread-spectrum modulation), frequency division multiplexing, as well as others.
The forward link, for example, may define (i) a pilot channel on which the RAN may broadcast a pilot signal to allow UEs to detect wireless coverage, (ii) system parameter channels (e.g., an overhead channel) on which the RAN may broadcast system operational parameters for reference by UEs so that the UE can then seek network access, (iii) paging channels on which the RAN may broadcast page messages to alert UEs of incoming communications, and (iv) traffic channels on which the RAN may transmit bearer traffic (e.g., application data) for receipt by UEs. And the reverse link, for example, may define (i) access channels on which UEs may transmit “access probes” such as registration messages and call origination requests, and (ii) traffic channels on which UEs may transmit bearer traffic for receipt by the RAN.
In operation, when a RAN seeks to communicate with a UE (e.g., to establish an incoming voice call or transmit incoming packet data), the RAN may first page the UE on a paging channel. The purpose of paging the UE may be to determine whether the UE is still within range of a wireless coverage area, and if so, to notify the UE of the incoming communication, and perhaps assign a traffic channel to the UE. To carry out a page, the RAN may transmit to the base station that is currently serving the UE some indication of the reason for the page (e.g., that there is an incoming call or data packet directed to the UE). In turn, the serving base station may use this indication to generate a page record, which the base station may transmit to the UE in one way or another. The UE may then reply to the base station with a page-response message (PRM), or some other message indicating successful receipt of the page record.
Given the scarcity of paging channel resources, some wireless communication networks implement a “zone-based” paging scheme. In such a scheme, the base stations in the RAN are divided into tracking areas, each with a respective tracking area ID. To facilitate paging on a zone basis, each base station in the RAN may broadcast as one of its overhead parameters the tracking area ID for the tracking area in which the base station is located. A UE operating in the network may then programmatically monitor the tracking area IDs specified in the overhead messages and may register with the network by, for example, transmitting to the RAN a “tracking area update” message when the UE detects that it has moved into a new tracking area (or for other reasons).
A RAN entity that facilitates paging (such as a switch), may collect and store (in a database, for example) these tracking area update messages as a way to keep track of the tracking areas in which the UEs are located. When a switch or other RAN component seeks to page a certain UE, the switch or other component may then refer to the database and send the page message to just those base stations that are within the tracking area of the UE's most recent registration.